Contents
Unit 1. Cell Structure and Microscopy
1. History of Cells………………………………………………………………….... 2
2. Why cells?..................................................................................................... 3
3. Cell Biology and Microscopy…………………………………………………..... 4
4. Animal and Plant cells have features in common…………………………….. 5
5. Differences between animal and Plant cells……………………………………5
6. Units of measurements………………………………………………………….. 6
7. Electron Microscopy……………………………………………………………… 11
8. Ultrastructure of an Animal Cell…………………………………………………. 13
9. Ultrastructure of a Plant Cell…………………………………………………….. 19
10. Two fundamentally different types of cells……………………………………… 21
11. Summary…………………………………………………………………………… 22
12. End of Chapter Questions……………………………………………………….. 23
Guided Worksheet for Calculating Linear Magnification
1. Magnification, Size, and Scale Bars………………………………………………. 27
2. Calculating Magnification of an Image Using it's Scale Bar…………………….. 28
3. Calculating Actual size of Specimen Using it's Scale Bar………………………. 29
4. Calculating specimen size using magnification of an image……………………. 30
More Practice on Calculating
1. Magnification…………………………………………………………………………. 32
2. Actual Size……………………………………………………………………………. 34
Past Paper Questions on Linear magnification…………… 37-40
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Magnification, Size, and Scale Bars
Cells are extremely small but knowing the sizes of objects viewed under the microscope can be really useful.
For example, a plant scientist might want to compare the relative sizes of pollen grains from plants in the
same genus to identify to help identify different species.
With a compound microscope, the magnification is the product of both lenses, so if microscope has a 10x
eyepiece and an 40x objective, the total magnification is 400x.
Magnification is defined as the ratio of the size of the image to the size of the object.
Magnification =
Image size
Actual size
Image
Size
The relationship between these three values can be
shown using the equation triangle to the right,
which offers a quick way of rearranging the values
in order to derive related formulas.
Actual
Size
Magnification
We use micrometers for specimen size under the microscope. The conversion is:
1mm = 1000 μm (micrometers)
Complete the following Chart:
Actual Specimen Size
Image (Drawing) Size
0.5 mm
2 cm
200 m
1 cm
40 m
2 cm
100 m
100m
200X
5 cm
100X
4 cm
50X
10mm
4mm
3X
10cm
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Magnification
25X
Calculating Magnification of an Image Using it's Scale Bar
Magnification= 320x
1. Calculate the magnification the cell. (show work)
Answer____________________
2. Calculate the magnification of the cilia base.
(show work)
Answer___________________
2
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3. Calculate the magnification of the
plant cell. (show work)
Answer_________________
Calculating the Size of a Specimen Using it's Scale Bar
4. Calculate the size of the mitochondria.
(show work)
Answer________________
3
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5. Calculate the size of a cilia. (show work)
Answer____________________
6. Calculate the size of the chloroplast.
(show work)
Answer__________________________
Calculating specimen size using magnification of an image
4
30
7. Calculate the size of the ant. (show work)
150x
Answer_____________________
8. Calculate the size of the nucleus. (show
work)
15000x
Answer___________________
9. Calculate the size of the Golgi apparatus.
(show work)
20000x
Answer______________________
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Magnification
Step 1)
Measure the image size using a ruler in
millimetres (mm)
Step 2)
Convert the millimetres (mm) into
micrometres (µm)
Step 3)
Divide your answer by the actual size
Question 1
This is a fly. Its actual eye size is 1,000µm.
What is the magnification?
1) Length of eye is ________ mm
2) _______ mm x1000 = _________ µm
3) Image size = _________ µm
4) Magnification = Image ÷ Actual
Magnification = _____ µm ÷ _____ µm
Magnification = ________
The picture shows the eye magnified (zoomed in) by ________ times.
Question 2
This is a red blood cell. Its actual size is
300µm. What is the magnification?
1) Length of cell is ________ mm
2) _______ mm x1000 = _________ µm
3) Image size = _________ µm
4) Magnification = Image ÷ Actual
Magnification = _____ µm ÷ _____ µm
Magnification = ________
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The picture shows the cell magnified (zoomed in) by ________ times.
Question 3
This is a snowflake. Its actual height is 700µm.
What is the magnification?
1) Length of snowflake is ________ mm
2) _______ mm x1000 = _________ µm
3) Image size = _________ µm
4) Magnification = Image ÷ Actual
Magnification = _____ µm ÷ _____ µm
Magnification = ________
The picture shows the snowflake magnified
(zoomed in) by ________ times.
Question 4
This is an insect. Its wings are 2,500µm.
What is the magnification?
1) Length of wing is ________ mm
2) _______ mm x1000 = _________ µm
3) Image size = _________ µm
4) Magnification = Image ÷ Actual
Magnification = _____ µm ÷ _____
µm
Magnification = ________
The picture shows the wing magnified (zoomed in) by ________ times.
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Question 5
This is a chloroplast. Its actual length is
50µm. What is the magnification?
1) Length of chloroplast is ________
mm
2) _______ mm x1000 = _________ µm
3) Image size = _________ µm
4) Magnification = Image ÷ Actual
Magnification = _____ µm ÷ _____
µm
Magnification = ________
The picture shows the chloroplast magnified (zoomed in) by ________ times.
Actual Size
Step 1)
Measure the image size using a ruler in
millimetres (mm)
Step 2)
Convert the millimetres (mm) into
micrometres (µm)
Step 3)
Divide your answer by the magnification
Question 1
This is a mosquito stinger. The
magnification is x4. What is the actual size?
1) Length of stinger is ________ mm
2) _______ mm x1000 = _________ µm
3) Image size = _________ µm
4) Actual size = Image ÷ Magnification
Actual size = ______ µm ÷ _____
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Actual size = ________
The actual size of this stinger is _____ µm. We can see it because it has been magnified.
Question 2
This is shark skin. It is made of teeth.
The magnification is x50. What is the
actual size of 1 tooth?
1) Length of tooth is ________ mm
2) _______ mm x1000 = _________ µm
3) Image size = _________ µm
4) Actual size = Image ÷ Magnification
Actual size = ______ µm ÷ _____
Actual size = ________
The actual size of this tooth is _____ µm. We can see it because it has been magnified.
Question 3
This is a grain of salt. The magnification is
x100. What is the actual size of the salt?
1) Size of salt is ________ mm
2) _______ mm x1000 = _________ µm
3) Image size = _________ µm
4) Actual size = Image ÷ Magnification
Actual size = ______ µm ÷ _____
Actual size = ________
The actual size of this salt is _____ µm. We can see it because it has been magnified.
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Question 4
This is a needle and thread. The magnification is x4.
What is the actual size of the needle?
1) Size of needle is ________ mm
2) _______ mm x1000 = _________ µm
3) Image size = _________ µm
4) Actual size = Image ÷ Magnification
Actual size = ______ µm ÷ _____
Actual size = ________
The actual size of this needle is _____ µm. We can see it because it has been magnified.
Question 5
This is a ballpoint pen. The
magnification is x20. What is the actual
size of the ballpoint pen?
1) Size of pen is ________ mm
2) _______ mm x1000 = _________
µm
3) Image size = _________ µm
4) Actual size = Image ÷ Magnification
Actual size = ______ µm ÷ _____
Actual size = ________
The actual size of this ballpoint pen is _____ µm. We can see it because it has been
magnified.
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Theory (structured) Questions On Linear Magnification :1.
(a) Name the structures ​A​, B
​ ​and ​C.​
[3]
(b) State the function of structure ​C​.
[1]
(c) Explain why structure ​C​ cannot be seen with a light microscope.
[2]
(d) State ​two ​disadvantages of the electron microscope compared to the light microscope for
the study of cells.
[2]
(e) Calculate the ​magnification​ of the image in Fig.1.1
Show your working and calculate the answer to the nearest whole number.
Answer= ……………………....[2]
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2.
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3.
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4. The drawing below shows the structure of a chloroplast.
a. Name structures labelled​ A ​to ​E,​ on the diagram.
(5)
(b) Describe ​three ​similarities in the structure of chloroplasts and mitochondria. (3)
(c) The chloroplast shown in the drawing was magnified 8500 times. Calculate the actual length
of the chloroplast along axis ​XY​. ​Show your working a
​ nd express your answer in micrometers.
(2)
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